case study 2 Flashcards
(27 cards)
What triggered the original Sigma Plan?
The 1953 storm surge which caused over 1,800 deaths.
What delayed the Flemish response until 1976?
Another severe storm that caused flooding in Ruisbroek, Walem, and Kastel.
How did the estuary’s historical evolution increase flood risk?
Poldering reduced estuary size, increasing tidal penetration.
What does Flanders Hydraulics Research account for in storm analysis?
Historical data, sea level rise, and nodal cycle corrections.
What TAW level was reached in the 1953 storm?
7.77 m (would be 8.16 m today).
What were the key measures in the original Sigma Plan (1977)?
Dike heightening, FCAs, and proposed storm surge barrier.
What is a Flood Control Area (FCA)?
Controlled overflow basin with lower overflow and higher ring dike.
Was the proposed storm surge barrier built?
No, it was deemed too complex and costly.
Why was the Sigma Plan updated after 2001?
Due to sea level rise, aging infrastructure, and the need for a risk-based approach.
What does a risk-based approach combine?
Frequency of events and potential damage.
What alternatives were evaluated in the updated plan?
Storm surge barrier, new estuary links, more FCAs, and dike strengthening.
What was included in the final updated Sigma Plan?
Dike reinforcements, more FCAs, depoldering, and ecological designs.
What is a Controlled Reduced Tidal Area (CRTA)?
Allows water in every tide, creating small tidal range for habitat development.
What are the benefits of CRTAs?
Support tidal flats, salt marshes, and biodiversity habitats.
What are wetlands used for in the Sigma Plan?
Non-tidal flood zones that improve ecological connectivity.
What is the role of Lippenbroek?
Pilot CRTA + FCA, functional for both flood and ecology.
What does the Vlassenbroek site include?
A CRTA and wetland, located ~110 km from estuary mouth.
When was the KBR FCA completed?
In 2015.
What was the impact of KBR’s completion?
Improved protection from 1-in-70y to 1-in-350y storm.
What was the original flood protection goal?
1-in-10,000-year storm (with surge barrier).
What is the mid-range sea level rise scenario by 2100?
+60 cm.
What does a +60 cm rise change storm frequency to?
A 1-in-370y storm becomes 1-in-23y.
Why is adaptive planning important?
To handle climate extremes and sea level rise.
What is used for storm surge modeling?
2D and 1D hydrodynamic models.
